The present invention relates, in general, to electrode probe assemblies and methods for mapping and/or ablating body tissue, and, in particular, to electrode probe assemblies and methods for mapping and/or ablating pulmonary vein tissue.
Aberrant conductive pathways can develop in heart tissue and the surrounding tissue, disrupting the normal path of the heart""s electrical impulses. For example, anatomical obstacles, called xe2x80x9cconduction blocks,xe2x80x9d can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets disrupt the normal activation of the atria or ventricles. The aberrant conductive pathways create abnormal, irregular, and sometimes life-threatening heart rhythms called arrhythmias. An arrhythmia can take place in the atria, for example, as in atrial tachycardia (xe2x80x9cATxe2x80x9d) or atrial fibrillation (xe2x80x9cAFxe2x80x9d). The arrhythmia can also take place in the ventricle, for example, as in ventricular tachycardia (xe2x80x9cVTxe2x80x9d).
In treating arrhythmias, it is sometimes essential that the location of the sources of the aberrant pathways (called focal arrhythmia substrates) be located. Once located, the focal arrhythmia substrate can be destroyed, or ablated, e.g., by surgical cutting or the application of heat. In particular, ablation can remove the aberrant conductive pathway, thereby restoring normal myocardial contraction. An example of such an ablation procedure is described in U.S. Pat. No. 5,471,982 issued to Edwards et al.
Alternatively, arrhythmias may be treated by actively interrupting all of the potential pathways for atrial reentry circuits by creating complex lesion patterns on the myocardial tissue. An example of such a procedure is described in U.S. Pat. No. 5,575,810, issued Swanson et al.
Frequently, an arrhythmia aberration resides at the base, or within one or more pulmonary veins, wherein the atrial tissue extends. To treat such an aberration, physicians use multiple catheters to gain access into interior regions of the pulmonary vein tissue for mapping and ablating targeted tissue areas. A physician must carefully and precisely control the ablation procedure, especially during procedures that map and ablate tissue within the pulmonary vein. During such a procedure, the physician may introduce a mapping catheter to map the aberrant conductive pathway within the pulmonary vein. The physician introduces the mapping catheter through a main vein, typically the femoral vein, and into the interior region of the pulmonary vein that is to be treated.
Placement of the mapping catheter within the vasculature of the patient is typically facilitated with the aid of an introducer guide sheath or guide wire. The introducer guide sheath is introduced into the left atrium of the heart using a conventional retrograde approach, i.e., through the respective aortic and mitral valves of the heart. Alternatively, the introducer guide sheath may be introduced into the left atrium using a transeptal approach, i.e., through the atrial septum. In either method, the catheter is introduced through the introducer guide sheath until a probe assembly at a distal portion of the catheter resides within the left atrium. A detailed description of methods for introducing a catheter into the left atrium via a transeptal approach is disclosed in U.S. Pat. No. 5,575,810, issued to Swanson et al., which is fully and expressly incorporated herein by reference. Once inside the left atrium, the physician may deliver the probe assembly into a desired pulmonary vein by employing a steering mechanism on the catheter handle. The physician situates the probe assembly within a selected tissue region in the interior of the pulmonary vein, adjacent to the opening into the left atrium, and maps electrical activity in the pulmonary vein tissue using one or more electrodes of the probe assembly.
After mapping, the physician introduces a second catheter to ablate the aberrant pulmonary vein tissue. The physician further manipulates a steering mechanism to place an ablation electrode carried on the distal tip of the ablation catheter within the selected tissue region in the interior of the pulmonary vein. The ablation electrode is placed in direct contact with the tissue that is to be ablated. The physician directs radio frequency energy from the ablation electrode through tissue to an electrode to ablate the tissue and form a lesion.
Problems with this approach include the possibility of misdirecting or misplacing the ablation electrode and inadvertently ablating non-aberrant, i.e., healthy, pulmonary vein tissue. Further, this approach is time-consuming because the physician has to introduce and remove two catheters. This leads to more patient discomfort and room for physician error. Poorly controlled ablation in the pulmonary vein can result in pulmonary vein stenosis. The pulmonary vein stenosis can lead to pulmonary hypertension, pulmonary edema, necrosis of lung tissue, and even complete pulmonary failure of a lung or lung lobe. In severe and rare cases, the only treatment may be a lung transplant.
The present invention includes the following three main aspects that solve the problems with separate mapping catheters and ablation catheters for mapping electrical activity in pulmonary vein tissue and ablating the pulmonary vein tissue: 1) a probe assembly with a microporous ablation body used with a basket assembly for mapping and ablating pulmonary vein tissue; 2) a probe assembly with a basket assembly for mapping and ablating pulmonary vein tissue; and 3) a probe assembly with an expandable body used with a basket assembly for mapping and ablating pulmonary vein tissue. Each of these aspects is summarized in turn below.
A first aspect of the invention includes a probe assembly for mapping and ablating pulmonary vein tissue. The probe assembly includes an expandable and collapsible basket assembly including multiple splines, one or more of the splines carrying one or more electrodes adapted to sense electrical activity in the pulmonary vein tissue, the basket assembly defining an interior, a microporous expandable and collapsible body disposed in the interior of the basket assembly and defining an interior adapted to receive a medium containing ions, an internal electrode disposed within the interior of the body and adapted to transmit electrical energy to the medium containing ions, the body including at least one microporous region having a plurality of micropores therein sized to pass ions contained in the medium without substantial medium perfusion therethrough, to thereby enable ionic transport of electrical energy from the internal electrode, through the ion-containing medium to an exterior of the body to ablate pulmonary vein tissue. In an exemplary implementation of the first aspect, the microporous expandable and collapsible body is adapted to be maintained in an expanded condition at a substantially constant pressure by a continuous flow of the medium through the body, providing a cooling effect in the microporous body and the pulmonary vein tissue.
A second aspect of the invention involves a probe assembly for mapping and ablating pulmonary vein tissue. The probe assembly includes an expandable and collapsible basket assembly including multiple splines, one or more of the splines carrying one or more electrodes, and at least one of the one or more electrodes adapted to sense electrical activity in the pulmonary vein tissue and ablate the pulmonary vein tissue.
A third aspect of the invention includes a probe assembly for mapping and ablating pulmonary vein tissue. The probe assembly includes an expandable and collapsible basket assembly including multiple splines, one or more of the splines carrying one or more electrodes adapted to sense electrical activity in the pulmonary vein tissue, the basket assembly defining an interior, and a non-porous expandable and collapsible body disposed in the interior of the basket assembly and defining an interior adapted to receive a fluid medium for expanding the expandable and collapsible body to exclude blood from the electrodes. In an exemplary implementation of the third aspect, the non-porous expandable and collapsible body is adapted to be maintained in an expanded condition at a substantially constant pressure by a continuous flow of the medium through the body, providing a cooling effect in the body and the pulmonary vein tissue.